Morning (it was when I started typing this) ,

While reading through intense (expensive) project builds on here I notice they all follow similar suit including the fuel systems & I was wondering if someone could shed some light on the following please...


Injectors: I am lead to believe 650cc injectors should suit a basic STI (stock being 565cc?) with an MD321 turbo for around 400/400 & you shouldn't go too big just for the sake of it. From then on Bigger turbo / cams / displacement etc then more fuel & bigger injectors to flow the required volume

To put this into perspective Brown Pants Racing (who's busy & probably doesn't want my stupid questions in his thread) has selected 1050cc injectors for his build for which he's aiming for 420-450 which seems like quite a big jump from 650cc. I would have thought (not fully understanding the requirements) that 850cc would have given more wriggle room, where 1050cc seems a big jump?

So either:
A) There's another reason why the injectors are so large (running a high boost level for instance)?
B) Oversized injectors aren't an issue & it to support further upgrades down the line
C) Something else?

*Disclaimer: BPR used as an example only as I am following his thread with great interest, just trying to learn, not calling him out on anything (I understand that was probably obvious but this is the internet )


Fuel Rails: I am guessing the stock fuel hose & lines can't hack bigger turbo pressures so are upgraded to billet rails with -6 / -8 fittings & lines to suit. Q: At what spec build (power wise) of build should you consider upgrading the fuels lines & rails.


Fuel Pressure Regulator: As above... I am guessing the stock one doesn't have -6 or -8 fittings & only hacks a certain amount of pressure which will become surpassed in the quest for low MPG


Series vs. Parallel: It seems the stock setup feeds the fuel rails in series (fuel feeds one rail, then then other in a loop with a single return, switching to parallel so the feed is split & feeds both individually & then both returns join back into a single return line - I am guessing all upgraded rail & hose setups use this method?


Swirl pot: What the hell is a swirl pot


Just over hear trying to learn the logic (mainly at what stage /power / boost level of a build supporting mods are required).

Cheers

 

Cant answer all your questions but 650cc will be fine for 400hp. I once used 555cc Nismo injectors and acheived 394hp with an SC38.

Fuel lines arent directly related to turbo pressure.

Aftermarket FPR's are fitted to run higher fuel pressure

Parallel running is done by people that think the last cylinder in the line is effectively leaned/starved by the previous 3 injectors. I did it once. I'm not doing it onmy current 450ish build.

Swirl pot is a (usually tall and narrow) container installed between you fuel tank and your fuel filter and are used to combat fuel surge. Under hard cornering or acceleration, fuel can be moved away from the lift pump and this causes issue fuel supply then leaning mix then det then boom . The pot offers an tank of uninterrupted fuel due to its dimensions with feed on top and discharge out the bottom.

 

the reason BrownPants has 'jumped' to 1050cc injectors is purely down to the quality and cost effectiveness of the injectors he has chosen........

with modern high quality injectors there is no downside using 1050's even on a std engine - this does NOT apply to all makes / variants so do your research properly

 

The 1050x injectors are supposed to be excellent - I'm tempted myself, and I'm probably as cheap as we come

 

I am also going back to OEM fuel rails for my 400ish build.

I modified the stock fuel rails for parallel delivery, but I'm not sure that there is much benefit (if any) at the levels talked about here, so going OEM again for neatness and less non hardline fuel hoses in the engine bay.

 

 

Just seen this! Sorry I missed out on the chat. Stockcar above summarised it well, the ID1050 injectors are really good and can be controlled easily by the ECU. I also wanted new injectors rathe rthan older re-flowed or de-capped injectors which is an option SC offered me.

Alyn @ AS has been a really helpful contact throughout my build with some brilliant advice. I can't recommend him enough to be honest. Give him a bell and have a chat, he doesn't bite!

 

You can fit an aftermarket FPR without ripping out the rails. Thats what i'm doing. You just need an adaptor to fit the end of the rail and run a hose from there to the FPR. Or you could braize on a fitting of your choosing to your rails.

For me, i'd need to be chasing +500hp to start going down the road of going parallel and aftermarkt rails. How much power are you planning to build for?

 

can somebody explain the rising rate regulators please? ive been looking at various fpr's like sytec/rcm/perrin etc and i remember somebody saying i need a rising rate one but they dont seem to to say which ones are and are not

 

That's what I'm doing. I'm sticking with the standard rails and fitting a Perrin FPR to boost the pressure as required. Will be fine for my levels.

 

As above easily controlled good idle well worth the expense.

 

Same as me.

 

1000's are a bit big for 400, I'm having 1000's in mine for 500. But it can vary from car to car, nines currently on stock hawk sti injectors and it's on 95% duty at 330bhp so very little left to give.

 

Currently not planning anything extreme, just trying to get my head around what's what...

While I can appreciate how much (time, money & headache) goes into a big power build I don't always understand what role every part plays.

So I am just asking stupid questions until I am no longer stupid


Cheers

 

not asking what you don't understand is true stupidity.